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sampling.cpp
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#include "sampling.h"
llama_sampling_context::~llama_sampling_context() {
for (auto & it : sequence_contexts) {
if (it.second.grammar != NULL) {
llama_grammar_free(it.second.grammar);
it.second.grammar = NULL;
}
}
}
llama_sampling_context llama_sampling_context_init(
const struct gpt_params & params,
llama_grammar * grammar) {
llama_sampling_context result;
result.params = params.sampling_params;
result.grammar = grammar;
return result;
}
// Note: Creates the context if it doesn't exist, so this always return something.
llama_sampler_sequence_context & llama_sampling_get_sequence_context(
llama_sampling_context & ctx_sampling,
const llama_seq_id seq) {
const auto it = ctx_sampling.sequence_contexts.find(seq);
if (it != ctx_sampling.sequence_contexts.end()) {
return it->second;
}
llama_sampler_sequence_context new_ctx = {
2.0f * ctx_sampling.params.mirostat_tau,
ctx_sampling.grammar != NULL ? llama_grammar_copy(ctx_sampling.grammar) : NULL,
};
return ctx_sampling.sequence_contexts.insert({seq, new_ctx}).first->second;
}
bool llama_sampling_context_reset(
llama_sampling_context & ctx_sampling,
const llama_seq_id seq) {
const auto it = ctx_sampling.sequence_contexts.find(seq);
if (it == ctx_sampling.sequence_contexts.end()) return false;
if (it->second.grammar != NULL) {
llama_grammar_free(it->second.grammar);
it->second.grammar = NULL;
}
ctx_sampling.sequence_contexts.erase(it);
return true;
}
llama_token llama_sampling_sample(
struct llama_context * ctx,
struct llama_context * ctx_guidance,
struct llama_sampling_context & ctx_sampling,
const std::vector<llama_token> & last_tokens,
std::vector<llama_token_data> & candidates,
const int idx,
llama_seq_id seq) {
const int n_ctx = llama_n_ctx(ctx);
const int n_vocab = llama_n_vocab(llama_get_model(ctx));
const llama_sampling_params & params = ctx_sampling.params;
const float temp = params.temp;
const int32_t top_k = params.top_k <= 0 ? n_vocab : params.top_k;
const float top_p = params.top_p;
const float tfs_z = params.tfs_z;
const float typical_p = params.typical_p;
const int32_t repeat_last_n = params.repeat_last_n < 0 ? n_ctx : params.repeat_last_n;
const float repeat_penalty = params.repeat_penalty;
const float alpha_presence = params.presence_penalty;
const float alpha_frequency = params.frequency_penalty;
const int mirostat = params.mirostat;
const float mirostat_tau = params.mirostat_tau;
const float mirostat_eta = params.mirostat_eta;
const bool penalize_nl = params.penalize_nl;
llama_token id = 0;
float * logits = llama_get_logits_ith(ctx, idx);
// Apply params.logit_bias map
for (auto it = params.logit_bias.begin(); it != params.logit_bias.end(); it++) {
logits[it->first] += it->second;
}
candidates.clear();
for (llama_token token_id = 0; token_id < n_vocab; token_id++) {
candidates.emplace_back(llama_token_data{token_id, logits[token_id], 0.0f});
}
llama_token_data_array cur_p = { candidates.data(), candidates.size(), false };
if (ctx_guidance) {
llama_sample_classifier_free_guidance(ctx, &cur_p, ctx_guidance, params.cfg_scale);
}
// apply penalties
if (!last_tokens.empty()) {
const float nl_logit = logits[llama_token_nl(ctx)];
const int last_n_repeat = std::min(std::min((int)last_tokens.size(), repeat_last_n), n_ctx);
llama_sample_repetition_penalty(ctx, &cur_p,
last_tokens.data() + last_tokens.size() - last_n_repeat,
last_n_repeat, repeat_penalty);
llama_sample_frequency_and_presence_penalties(ctx, &cur_p,
last_tokens.data() + last_tokens.size() - last_n_repeat,
last_n_repeat, alpha_frequency, alpha_presence);
if (!penalize_nl) {
for (size_t idx = 0; idx < cur_p.size; idx++) {
if (cur_p.data[idx].id == llama_token_nl(ctx)) {
cur_p.data[idx].logit = nl_logit;
break;
}
}
}
}
llama_sampler_sequence_context & ctx_seq = llama_sampling_get_sequence_context(ctx_sampling, seq);
if (ctx_seq.grammar != NULL) {
llama_sample_grammar(ctx, &cur_p, ctx_seq.grammar);
}
if (temp <= 0) {
// Greedy sampling
id = llama_sample_token_greedy(ctx, &cur_p);
} else {
if (mirostat == 1) {
const int mirostat_m = 100;
llama_sample_temp(ctx, &cur_p, temp);
id = llama_sample_token_mirostat(ctx, &cur_p, mirostat_tau, mirostat_eta, mirostat_m, &ctx_seq.mirostat_mu);
} else if (mirostat == 2) {
llama_sample_temp(ctx, &cur_p, temp);
id = llama_sample_token_mirostat_v2(ctx, &cur_p, mirostat_tau, mirostat_eta, &ctx_seq.mirostat_mu);
} else {
// Temperature sampling
size_t min_keep = std::max(1, params.n_probs);
llama_sample_top_k (ctx, &cur_p, top_k, min_keep);
llama_sample_tail_free (ctx, &cur_p, tfs_z, min_keep);
llama_sample_typical (ctx, &cur_p, typical_p, min_keep);
llama_sample_top_p (ctx, &cur_p, top_p, min_keep);
llama_sample_temp(ctx, &cur_p, temp);
{
const int n_top = 10;
LOG("top %d candidates:\n", n_top);
for (int i = 0; i < n_top; i++) {
const llama_token id = cur_p.data[i].id;
(void)id; // To avoid a warning that id is unused when logging is disabled.
LOG(" - %5d: '%12s' (%.3f)\n", id, llama_token_to_piece(ctx, id).c_str(), cur_p.data[i].p);
}
}
id = llama_sample_token(ctx, &cur_p);
LOG("sampled token: %5d: '%s'\n", id, llama_token_to_piece(ctx, id).c_str());
}
}
if (ctx_seq.grammar != NULL) {
llama_grammar_accept_token(ctx, ctx_seq.grammar, id);
}
return id;
}